Two-cycle multicylinder internal-combustion engine



Nav. 3, 1925. 1,559,997

F. o. SHEPHERD Two-CYCLE mumlcumpa INTERNAL coMus'rIoN ENGINE l Film1 'July :22, 1921 l zsheets-shen 1 Nov. 3 l 1925. l 1,559,997

v F. D. SHEPHERD u Tw-CYGLE MULTIGYLINDHR INTERNAL coMus'rIoN ENGINE July 22 1921 c? .42 43 44 2 Sheets-Sheet 2 f Patented N ov. *3,1 1925.

UNITED ks'iii'iizs FRANK .'D. SHEPHERD, 0F SALT LAKE CITY, UTAH.

TwocYcLE MULTICYLINDER .INTERNAL-connus'rion ENGINE.

.Application filed July 22, 1921. Serial No. 486,681.'

To 'all 'whom t may concern:

Be it known that I, FRANK D. SH'PHERD, residing at Salt Lake City, county of Salt Lake, and State of'Utali, -a citizen of the United States, havey invented certain new and useful Improvements in rINNO-Cycle Multicylinder Internal-Combustion Engines, of which the following is a specifica-V lMy invention relates to internal combustion yengines and in what I regardas the best and completestQ embodiment of my invention' relates to two-cycle iniilticylinderl engines, some of my objects being maximum utilization of fuel energ certainty ot' a full charge ot' mixture for supply to the cylinder for they power stroke'thorou'gli scavenging of the burnt gases and hence assurance o f the purity ofthe charge as faras contamination by residual gases in the cylinder is concerned, eonipactness of structure, and

withal extreme simplicityof parts. Other.

.objects attained lby and advantages o f my invention will appear from the detail de scription hereinafter given or will be understood or appreciated by those skilled in theart, My invention accordingly consists in an internal combustion. engine having the construction 'described by or embraced within the scope or meaning vof the appended claim. In the annexed drawings: f Fig.V 1 is ajviewpaitly in side' elevation and partly in vertical section of a four cylinder. two-cycle engine embodying my iii-1 vention;

Fig 2 Fig..3 isa detail view in elevation from the-inner side ofthe plate which contains or forms part of the transferpassages between 'the cylinders of a connected pair;

' Fi' 4 isa detail vView in sectionA showing a .di erentv form of inlet controlling or suc- 'tion'valve'from that shown in Figs. l and 2;

Fig. 5 vis a detail view in section of an 'embodiment of my invention in which no transfer controlling `valve `is employed.

' `The embodiment o f my invention-.shown 'in-the drawings-is an internal combustion engine for motor vehicles, but it is to be understood vthat I do not restrict4 myself only to such an engine,and it is also tobe understood that while tliezexi'gine shown in the drawing'sis o f the water-cooled type, I,

'smaller diameter' than do not-confine myseli` to that type of engines undeistood that my inventionmay be yembodied in engines having other gas ignition means. It is also to be understood that I do not restrict myself to a four cylinder,

. engine as the number may bev more or less,

but the number should be either two or multiples of two in order to embody in: Ventron 1n what I now considerits most advantageous form.

The four cylinders designated, respecff. tively, l0, 11, 12, and 13, are cast en bloc with a single detachable head, 14, for the '70 four, a gas tight joint, of course, beingmade between the head and the cylinders, and. all of the cylinders open at the bottom into the crank case, 15, within whichfrotate the cranks vof the crankshaft, 16, but as will appear hereinafter by my invention the. gas is not `taken from the crank case andghencel the subdivision of the crank case into sepa` iateunits,'which is necessary in multi-cylinder'two-cy le engines that take gas from the 80 crank case, is avoided and so the objectionable length of a multi-cylinderengine due to such .subdivision or partitioning is avoided. .Moreover, b y the non-use of the H crank case asthe sourcefrom which the, gasA 8.5

is taken, I overcome one-of the objections.,` to 'the use :of two-.cycle'engines for motor vehicles which isthat idling speeds are impossible-because 'of inadequate compression is a secti'onionmthe line 2 2 of 90 fourcylinde'rs is exactly the same. Each has a `bore in two sections, one section being of the: other, the two sections being coaxial,

piston, 17,'being the large piston, 18, the andthe cylinders are connected bv-ports or of gas is passed from the cylinder of the charging Piston, 18, to the combustion chamber o the power piston, 17, of the ad 4 jacent cylinder. "The pistons of a thus connected pair of'cylindersare connectediiviti'i105 cranks, of the crank shaft, '16, ISOdegrees apar@ The ofthe fourpistenahowever-," are apart: v 'llius theinrrangement andeach section be*- 111g -itted with its own 'piston, .the small :v

is such that during the power stroke ofa .power (piston, 17, a charge of gasA will be 1. rawn through an inlet port, 19, into the cylinder of the chargingv piston, 18, of that power piston, 17, and simultaneously a vchange previously drawn into the cylinder of the adjacent charging piston, 18, will be carburetor, 22, of suitable construction,

which valve automatically opens on the surtion stroke of the charging cylinder piston and automatically closes on the transf'ei` stroke of that piston, the result of that arrangement being that the charging piston on its suction stroke d oes not work against or for the production of a high vacuum in order to cause the flow of a charge of mii;- ture into its cylinder preliminarvtotransfer to the associated power piston cylinder, and hence energy that would be consumed in the production of such a high vacuum is conserved.l Again, as the How of the mixture into the charging piston begins immediately after the start of AJthe charging` piston in the direction to produce the suction flow ofthe mixture and such flow continues unf'tifl ,the limit of travel of the piston in that diretztion is reached, thereris ample ,opportunity for a full supply of fuel mixture "to the-charging"cylinder before the transfer movement of its piston begins.

The suction valve arrangement is preferably that'shown in Figs. 1 and 2 the valve, 23, being'of the poppet-piston type, its piston,-24, tting the interior of a housing, 25,

' it to its seat.

and being engaged by one end of a coil spring, 26, that acts normally to. move the ,valveVv to lits seat, 27, and yieldinglyholds Of course, during the transfer travel of the charging piston a pressure is thereby produced. on the valve which tightly holds it to its seat so that hone of the gas of the charge.being'transferred to a lpower cylinder can pass back into the inlet manifold. Theother end of the valve scating spring, 26, bears against a disk, 2S, in the housing, 25, which disk is engaged by the inner end of a screw, 29, that passes through a threaded hole in the block or cap,

. 30, which closes the upper end of the housing, the adjusting screw being provided so 'that there may be necessary adjustment ot the pressure of theI spring to assure the movements of the valve, 23, with such nicety as the speed requirements of the engine may call for. To give the underside of the valve, 23, a greater area than that of the upper side of the piston, 24, the piston -is perforend with the charge outlet port, 32, from the v charging cylinder and at the other end with `the inlet port, 34, of the associated power cylinder. One of these` passages comprises a groove or channel, 35, in the outer-.side of the cylinder wall which is covered or 'closed onthe outer side by the flat surface` of a plate, 36, which is bolted to the cylinder side, while the other passage consists of a channel, 37, formed in the plate, 36A, this arrangement resulting in a compact structure free from objectionable lateral protrusion or projection from or at the side ofthe engine. the passage, 20, are preferably cast integrally with the plate, 36, so that all these parts are in one member which makes for simplicity' and inexpensiveness of construction and is further important in eliminating the presence of joints at points where imperfect joints would result in the escape of fuelmixture. It is in this connection that the eniployment of the pistontype valve shown in Figs. 1 and 2is important because the interior of the housing,'25, has a diameter suiciently large, compared with the di.- ameter of--the valve, 23,'to permit the assembly and removal of the valve through the lcontainer or housing. Thus the only joints are between the side of the plate, 36, and the cylinder and with the inlet manifold, 21.

The-inlet port, 34, in the embodiment of my invention shown in Figs. 1 and 2, leads to the top of the power cylinder through `a passage, 38, in the cylinder head, l4,con1- munication between the inlet port, 3 4, and

thev power cylinder being controlled by a poppetjvalve, 39, which normally is yield` ingly moved to itsseat, 40, by a coil spring, 41, in a housing', 42, projecting from the top of the head, 14, the Valve having a stem, 43,

`which reaches into such housing and which has a head, 44, against which the spring presses. The valve, 39, however is wholly automatic in its opening and closing movements, it opening when during the power stroke of a power piston, the pressure in the cylinder of such piston is reduced by rea sonv of the opening of the exhaust port, 45,

The housing, 25, and the walls of port, 34, and closing when the compressionstroke of s uch power' piston takes place. The tension of below the pressure inthe inlet the spring, 41, is adjustable by similar means l to what I show inthe case of the' suction valve spring,.26, that is vto say, the spring, 41, bears against a disk, 46, which 1s engaged by the. inner end of an adjusting screw, 47, passing through a threaded opening in the head or cap, 48, of the contamer or housing, 42', v

4The exhaust ports, 45, lead to a manifold 49, and the exhaust port, 45, in the case oli each power cylinder is opened -\and closed by the traveliof `the power piston of'that cylinder, the opening of the port, ofcourse,

zio,

beginning ust before the completion ofthe power stroke and the portaccordingly being at the opposite end of the.` power cylinder urtherest from vthe inlet port, 345 As"A a result of the relative arrangement' of inlet and exhaust ports and yby reason ofthe employvnient. of the transfer'co'ntrolling Tval've, 39,v

it is assured that 'thoroughr scavenging of the' burnt gasesshall take place without any substantial quantity thereof beingleft -to miX 'inlet ture under valve,

'haust port will be cut ciently soon to prevent vanyfsubstantial esH "haust port. At the instant Awith the incoming charge of freshv mixture'. During the power stroke of a'power piston the va ve, 39, willbe held' to its seat thus holding back in the transfer passage and the pressure 1n suchpassage and inlet port because -o' thetransfer travel of lthe charging piston so Athat when the poppet 39, eventually opens in consequence-of tllle uncovering of the exhaust port, 45, by t e or rush with, considerable velocity into the upper end of the 'power cylinder and with but little diminished velocity will flow down into the latter and thus most advantageously act upon the burnt gases to drive them out' of the exhaust port. AOn fthev return compression stroke of the power piston the exol' or covered Sullicape of the fresh mixture through the ex'- th'e power piston completes its power strokethe puppet-"valve,l

i power piston and 39, as shown inFig. 2,-"has not fully closed the inlet port, 34, but atonce. upon the beginning of the compression 'stroke of such, dueto the action of the spring, 41., thev v'alif'e, 39, seats and thus back flow of the fresh mixture that isv entering the power cylinder' is prevented. v

Each powerl piston; 17, has suitable pack-y ing rings, 50, and lubrication holding grooves, 51, the latter being situated so that at no time do they enter the adjacent,charg-l ing piston cylinders, the result beingthat the entire portion of the power piston that l enters the charging piston cylinder is smooth v and uninterrupte 05 but to, provide lubricatien for that portion of the power piston' I and thus readily port, 34, leading to such valvethe mix- "piston, 18, has suitable power piston, thefreshmixture will pop The'variou's ports'over which move are preferably off grid form, asshown Ais in reality a provide lubricant holding grooves, 52, in the walls ofthe power piston-cylinder, at the ends adjacent the charging piston cylinder. These grooves as well as those in the piston form, seals whichprevent the passage of gasesbetween the power and charging piston cylinders.

To facilitate assembling, the en'd of the power cylinder `where opens into the charging piston cylinder is chamfered at 53, so that the piston, 17, with its packing rings, 50, loosely .applied thereto may be inserted into its cylinder through th'eicharging cylinder, and such rings in a loose expanded state engaging the chamfered orl beveled surface will be squeezed or cammed into vposition enter the cylinder along with'the piston, 17. f

` y Each charging fpiston, 18, is of such length 'and the extent o .Awould be -throw-n onthe power'piston and like wear o n its cylinder occur, and opportunity afforded for gas communication be tween the charging piston cylinder and the crank case and between the two cylinders. I- find that to: secure this result the charging piston should have alength elal 'toat least substantially half its stroke. ach charging acking rings, 54, near `each end, and ubricant holding grooves, 55, near each/end.

the pistons in the drawings," to -prfovide narrow. slots 4thereby da r o'f'thel iston rin s catching on the ed lfthe polxt's 4is pree'nted.

It will e seenfthat a pair'of cylinders and the-two istons 'of each constitutetwo sets, as what cylinder. I Thusl for each 'set there is a `power charging piston' an a cylinder for each 'of piston .and a connected l (Nl instead of m opening" of extended'area and 4 have termed a cylinder section I suchpistons, and in the embodiment of my .invention illustrated in the drawings there' are really four sets of power and charging pistons and cylinders therefor.

' `When I employ four vcylinders and arrange them in pairs so that the pistons of cooperating pairs' are connected with the crank shaft 180"A apart, and that considering 90 apart, I fire the cylinders in the -order 1,'4, 2v and 3, because that prevents any ob'- jectionable unbalanced strains from the pisall four ,pistons the cranks are successively' I ton thrust on the crank shaft.. The result is due to the'fact'that with such an order of firing when, for example, cylinder #10 has fired and is exhausting, the piston of cylinto the cylinder and prevents its escape 5 der 13 is on the power stroke, and therefore exerting force in the same -direction on the crank shaft, the two points of application of the two forces in the saine direction being thus symmetrically situated with reference to the shaft bearings, and in like manner the two intermediate cylinders, when their pistons are under power, are simultaneously exerting power in the same direction on the crank shaft and at symmetrical distances from the Shaft bearings.

As' the. cranks are 90 apart and an explosion occurs at every fourth revolution of the crank shaft, the power is applied to the shaft in a smooth steady flow, and, hence, vibration of the shaftv is eliminated Thus as a result of this crank arrangement and the firing order described, the engine is of high efficiency and free from objectionable strains.

The top of the cylinder or combustionV chamber is formed by surfaces that are compound curves', the general shape of the chamber being that of a frustum of a cone with the spark plug, 140, at the apex, the surfaces next the spark plug being convex, and those in the lower part being concave,'a chamber being thus provided free from angular pockets or corners, and the surfaces against which the explosion reacts having such relation to the power end of the piston as to,

compel the direct application of the force of the expanding gas to the pistou, and by reason of the gradually enlarging space from the spark plug to the piston effecting Q a progressive ignition of thegas from the spark plug to the piston. As shown 1n Fig. 4 a suction valve, 57,

lmay be employed different in construction from the suction valve shown in Figs. 1 and 2. As said valve 57 has a downwardly projecting stem, S, and a spring container, 59, this necessitates a lateral projection, 60, from the plate.y G1, which contains o1.,forms part of the transfer openings for connection with the inletmanifold, so that it is not so desirable a construction as that shown in Figs. l and 2, because it is not so compact for it throws the manifoldandrarburetor a considerable distance to one side of the engine.

In Fig. 5, an embodiment of luy-invention is shown which dispenses with the transfer controlling valve, 39, by making the power piston. G2, control the inlet port, 63, tothe power piston e \,'linder, G4, the inlet port, 63, being thus vlocated at the bottom of the power cylinderso as to be uncovered only Awhen the power strokeis finished. Inasmuch as in thiscase the inlet port, 63, and the exhaust port, (not shown in Fig. 5), are open at thesame time, the power receiving end of thel piston,62, has al rib, 65, that deiects the incoming' fresh mixture. upward inthrough the exhaust port. The suction valve arrangement shown in Fig. 5 is the same as that shown in Figs. 1 and 2, consisting of the valve, 66, with a piston, 67, in a container or housing, 68, in which the piston slides, the housing, 68, being cast integral withthe plate, 69, which contains or provides the transfer passages, 70.

It willbe observed that though valves are employed byv me, no cams are required to lift them from their seats and yet their operation is automatic, such operation being dependent upon the pressure in the cylinders produced by the travel ofthe pistons therein, the elimination of lifting cams thus re! sulting'in. simplification of the engine and heilig otherwise advantageous. The valves.

it will be seen, perform the functions of a check valve in that they permit flow of fluid in one direction while preventing its flow lin the opposite direction, although unlike the ordinary check valve, seating is not dependent upon pressure in the direction that would tend to seat them because it is important, as by means such as the seating springs, to cause the seating of the valves before any back flow of gas could take placel so as'to assure that no gas or mixture will be lost through the 'valves' when the pistons move in the direction to effect either the transfer of the mixture lfrom awcharging cylinder to a power cylinder or toleffect the compression of a charge newly introduced into a power cylinder.

It will be noted that the housing or container for the valve seating spring and the valve guiding piston or stem has no communication with the external air and hence even though by leakage past the piston or stem or passage through holes in the piston as in the valve shown in Figs. 2 and 5, gas might enter the container or housing, it could not escape therefrom and hence no loss of gas or pressure could occur.

It is to be understood that my invention may be embodied in engines with the various parts or members constructed and arranged differently from what- I illustrate in the drawings and may ble described with sonic detail, and the scope of my invention is to bev determined not by what I have shown and described but byv what is defined by or comprehended within the language or meaninfr of the following claim.

- Vhat I* claim is: f

An internalrombustion engine having two sets of cylinders, each setcomprising twoA cylinders and a piston for each cylinder, one piston being a power piston and the other a charging piston, the cylinder of the power piston having inlet and exhaust ports and the cylinder of the charging piston 'havingvinlet andoutlet ports, an `inlet to the,

' charging lpiston cylinder, a check valve co11- trolling-Howlthrough: said inlet, conduits connecting the outlet port vof each charging cylinder of oneset with the" inlet of each power cylinder of the othei` set, a; plate separate from the cylinders containin one of said conduits, the other condu1t being formed by "Ia channel in thev .cylinder Miall and an a'c'ljocent side of said plate, and hous'jings for .said valves inte In testimony whereof I hereunto aflix my signature.

FRANK D.' SHEPHERD.

gral With said plate, T10' 

